The present invention is a device for use when operating press or die casting equipment. More specifically, the present invention relates to a ram used to force back seized injection tips, ejector pins and the like on equipment such as die cast machines.
Die castings are some of the highest volume, mass-produced items manufactured by the metalworking industry. Die casting is a manufacturing method for processing accurately dimensioned, sharply defined, smooth or textured-surface metal parts. Die casting is accomplished by injecting molten metal under high pressure into reusable metal dies. Die casting is a fast, efficient, and economical process which, when used to its maximum potential, replaces assemblies of a variety of parts produced by various manufacturing processes at significant savings in cost and labor. Consequently, because time is critical to the success of a die casting operation, extraneous time spent forcing back stuck components on a die cast machine or removing stuck fragments of a casting from a die cavity is not desirable and can be costly.
Die casting dies are made of alloy tool steels and configured in at least two sections. These two sections are typically referred to as the fixed die half and ejector die half. The fixed die half is mounted on the side of the die cast machine toward a molten metal injection system. Molten metal enters the die through a shot sleeve located in the fixed die half.
The ejector die half is mounted on a movable platen of the die cast machine opposite the fixed die half. The ejector die half usually contains runners (passageways) and gates (inlets) which route the molten metal to the cavity (or cavities) of the die where the part is formed. The ejector die half is also connected to an ejector box which houses a mechanism for ejecting the die casting from the die. The die casting normally adheres to the ejector die half prior to ejection. Ejection occurs when pins, called ejector pins, move forward, to force the die casting from the die cavity.
Ejection typically occurs as part of the opening stroke of the die cast machine. The ejector pins are connected to what is typically referred to as an ejector plate within the ejector box. Connected to the ejector plate, parallel to the ejector pins, are return pins. The return pins return the plate to its casting position as the die closes. Thus, as the ejector plate returns to its casting position, the ejector pins are drawn out of the die cavity.
An injection tip, also known as an injection plunger, is used to force molten metal through the shot sleeve and into the cavity of the die. During the course of metal die casting, an injection tip can become seized in the shot sleeve. Seizure of an injection tip usually occurs when extreme pressure in the sleeve, which can exceed 15,000 psi, forces molten metal back into the space between the interior wall of the shot sleeve and the exterior of the injection tip. When an injection tip becomes seized in a shot sleeve, it becomes necessary to physically force the injection tip back into the sleeve in order to resume the die casting process. In order to physically force the injection tip back, the die cast machine must be stopped and an operator must access the space between the ejector die half and fixed die half.
The conventional way of forcing a seized injection tip back into the shot sleeve is to place a pin between the ejector die half and the head of the injection tip. This pin is usually made from brass or other soft metal in order not to damage the head of the injection tip or other part of the die cast machine. The ejector die half is then closed toward the fixed die half until it contacts the brass pin, wherein the force of the closing ejector die half is transferred through the brass pin to push the injection tip back into place. As the injection tip is pushed back, the solidified metal is forced out of the space between the injection tip and shot sleeve and the die casting cycle can then resume.
There are several problems with the conventional approach of using a brass pin to force the injection tip back. From a safety standpoint, the problems stem from positioning the brass pin in between the two die halves. The pin oftentimes must be held in position during the closure of the ejector die half to be certain that the pin contacts the head of the injection tip properly. Proper positioning avoids damage to the die halves and injection tip. Many machine operators have been injured when an operator has slipped or mispositioned the brass pin or the ejector die half has closed unexpectedly, crushing the hands of the operator in the process. Operators have also been injured when the die halves have closed too quickly while the operator was positioning the brass pin against the head of the injection tip. In addition, damage to the die halves, injection tip or other component can occur when the operator slips or mispositions the brass pin or the ejector die half closes unexpectedly or too quickly.
In addition, the conventional method of using a brass pin can be cumbersome and create costly delay in the die casting process by requiring the operator to slowly close the ejector die half while simultaneously positioning the pin on the head of the injection tip. In addition, the conventional method is costly because two operators are needed to force back the seized injection tip. One operator is needed to hold and position the brass pin while another operator is needed to operate the closing of the die casting machine. All of these slowdowns or delays are extremely costly as they negatively affect efficiency and throughput.
Another situation requiring the conventional method of using a brass pin to drive back a component of a die casting machine arises when an operator needs to force back ejector pins. Sometimes fragments of a cast product remain stuck in the die after the ejector die half pulls away from the fixed die half. When fragments do become stuck in the die, it is not possible to close the ejector die half. To resume the die cast process when this occurs, could damage either of the die halves or other components. In order to remove the fragments or stuck die casting, an operator needs to manually pry the fragment or casting from the fixed die half. This cannot be performed, however, unless the ejector pins protruding from the ejector die half are forced back and out of the way.
One conventional method for returning the ejector pins is to drive the return pins back by placing a brass pin between the return pin and the face of the fixed die half. The return pin is usually fixedly attached at one end to the ejector plate. The same ejector plate also has the ejector pins attached at one end in an array which is parallel to the return pin. To force back the ejector pins, the brass pin is placed between the end of the return pin opposite of the ejector plate and the face of the fixed die cast. The ejector die half is then closed toward the fixed die half until contact is made between the brass pin and both the return pin and the face of the ejector die half. The force of the closing die half is then transferred to the brass pin that, in turn, forces the return pins back, pushing back the ejector pins. Similar safety, economic and efficiency issues arise using the brass pin method in driving back ejector pins as those issues raised in driving back an injection tip. Specifically, damage or harm can occur to the die cast machine or the operator through misplacement of the brass pin or improper closing of the ejector die half. In addition, this process of driving back the return pin requires an operator to spend excess time aligning the brass pin with the return pin and holding the pin until contact is made between the pin, return pin, and fixed die half. Two operators are also required to force back the ejector pins. One operator must hold the brass pin in place while another operator operates the closing of machine.
Another conventional method to force back a seized injection tip or to drive back injector pins is to use a hammer or hammer with pin. The hammer could be brass or just the pin could be brass. This method requires an operator to physically strike the seized injector tip or ejector pins with a hammer or to strike with a hammer a brass pin placed adjacent the seized injection tip or ejector pin.
Striking the injection tip or ejector pins with a hammer is not safe because an operator can be injured by a misplaced blow with the hammer. In addition, a misplaced blow with a hammer can damage the injection tip, ejector pins or other components of the die cast machine.
The hammer method is also time consuming and sometimes not possible. Because of the limited space between the die halves, it is difficult for an operator to gain enough swing force to drive back the seized injection tip or ejector pin. Furthermore, in some situations, it is nearly impossible to even fit a hammer and brass pin or hammer alone between the die halves. Maneuvering a hammer and brass pin, therefore, can be cumbersome and time consuming and many times not feasible.
In summary, the conventional methods of forcing back an injection tip or ejector pins are not desirable. As mentioned, these conventional methods are time consuming, cumbersome, dangerous, potentially harmful to the operator and/or equipment, and sometimes simply not feasible.